SALEM -- Milk production in organic dairy herds averages 31 percent less than in conventional herds, according to a new study.

"This is probably related to feeding management more than anything else," said Mike Gamroth, an Oregon State University College of Animal Sciences professor.

Organic producers use about half the grain conventional producers use, he said.

Gamroth's report was based on results of a three-year study that involved dairy producers from Oregon, Wisconsin and New York. The study was conducted by the University of Wisconsin at Madison, Cornell University and OSU.

Researchers used a nearly $1 million grant from the USDA's Integrated Organic Program to collect and analyze the data, Gamroth said.

The study also showed organic dairy producers average less than one cow per acre, compared to more than two cows per acre for conventional producers.

"There is a significant difference in the amount of land set aside for grazing on organic farms," Gamroth said.

The study showed that organic producers generally were satisfied with disease treatments, except when it came to infectious diseases, like pneumonia.